Opium poppy cultivation has been almost eradicated in Asia's Golden Triangle, the border zone between Burma, Thailand and Laos that was once the world's most prolific supplier of opium, according to a report published by the United Nations yesterday.

The area of land being used for poppy farming has fallen by 22% worldwide, reflecting declines in the world's three biggest producers of opium: Afghanistan, Burma and Laos.

The UN's 2006 World Drug Report described south-east Asia as an "overlooked success story", where governments had succeeded in slashing poppy cultivation. Laos, once the world's third biggest heroin producer, declared itself free of poppy cultivation in February. It used a "carrot and stick" approach, striking agreements with farmers to stop growing poppies or risk seeing their fields destroyed. The Burmese government reduced the area under cultivation by 26% to 32,800 hectares (82,000 acres) last year.

But the report warned: "Sustaining these remarkable achievements may, however, largely depend on the availability of socio-economic alternatives for the farmers who have given up a source of their livelihood."

In an illustration of the difficulties, it emerged that even as the report was being published, new figures indicated a resurgence of poppy farming in Laos. Since February, an estimated 2,500 hectares have been brought back under poppy cultivation, driven by an opium price that has increased by 5% this year to $550 (£303) a kilo.

"The situation remains fragile, especially in the more vulnerable remote northern locations," said Antonio Maria Costa, executive director of the UN's Office on Drugs and Crime. "We need to ensure that this victory against drugs proves to be lasting."

In Afghanistan, the area of land under poppy cultivation fell last year for the first time since 2001, but the country still accounts for 89% of global production. The report said: "Within a few years, Asia's notorious Golden Triangle, once the world's narcotics epicentre, could become opium-free. But in Afghanistan, while the area under cultivation decreased in 2005, the country's drug situation remains vulnerable to reversal."

The UN report also revealed that ecstasy seizures have surged. Global seizures of the drug, which is mainly manufactured in Europe, passed eight tonnes in 2004, up from less than five in 2003. Global cocaine seizures reached a record high in 2004, up to 588 tonnes. The increase was the result of better cooperation between law enforcement agencies and the improved sharing of intelligence, the report said.

The area of coca cultivation in Colombia had been increasing, despite sustained US-backed eradication efforts since 2000. Colombia accounts for 54% of coca cultivation globally, followed by Peru (30%) and Bolivia (16%), according to the study.

Most cocaine continues to be used in the Americas, particularly North America, which accounts, with 6.5 million users, for almost half the global market, according to the report.

Cocaine use in Europe is rising. Almost 25% of cocaine users are in west and central Europe, the UN study said.

Consumption of cannabis, the most widely used illicit drug, continued to increase. An estimated 162 million people used cannabis in 2004.

Assessing the range of illicit drugs, from heroin to cocaine as well as marijuana, amphetamines and ecstasy, the report concluded: "Drug control is working and the world drug problem is being contained." Levels of cultivation and addiction are much lower than they were 100 years ago, it said.